Television system



Sep@ 29, w36- H. R. LUBCKE VTELEVISION SYSTEM Filed July 29, 1932 2Sheets-Slnel l fad/b fam/fb Sept 29, H936., H. R. LUBCKE l 2,055,748

TELEVISION SYSTEM Filed July 29, 1932 2 Sheets-ShamI 2 .D IP

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Inventor; #any R.Lbc]ce,

Per /f-M t Mgg Patented Sept. 29, 1936 UNITED STATES PATENT oFFlcETELEVISION SYSTEM Harry R. Lubcke, Los Angeles, Calif.

Application July 29, 1932. Serial No. 625,620

My invention relates to television systems, and more specifically tothose wherein both image transmission and synchronization areaccomplished over a single channel of communication from transmitter toreceiver.

In the practice of television, it is necessary to have the scanningdevices at the receiver and the transmitter operate exactly in step, sothat the specific light intensity of a given spot in the field of viewat the transmitter will be reproduced in the same relative position atthe receiver. This requires a coaction between the transmitter andreceiver, in addition to a proper response to the degree of light ordarkness of the elementary areas of the picture. This specificcoactiornis often obtained by utilizing a second channel of communication fromtransmitter to receiver, for the transmission of synchronizing pulses orfrequencies; or it is accomplished by operating the scanning devices onan alternating power supply that is common to both the transmitter andreceiver. Both of these methods have apparent disadvantages incomparison to one which transmits all the necessary impulses over asingle channel 'of communication. proved means for the accomplishment ofthis latter method, is one of the objects of this invention.

Another object is to provide a new and better method for combiningsynchronizingv pulses with the image pulses, to form a composite signalsent over the single channel of communication.

Another object is to provide simplified and efilcient means forselecting the synchronizing pulses from the composite signal at thereceiver, and for applying them to the scanning devices.

Still another object is to provide means for sharpening thesynchronizing or image pulses.

A further object of this invention is to remove from the synchronizingoutput certain spurious pulses, which may arise from imperfections inthe communication channel.

My objects have been attained in the manner illustrated in theaccompanying drawings, in which:-

Figure l is a diagrammatic representation-oi' a complete televisiontransmitting apparatus for transmitting images on motion picture nlm, inaccordance with the principles of my present invention;

Figure 2 similarly illustrates a complete television receivingapparatus;

Figure 3 is a diagram explanatory of my improved method for selectingthe synchronizing pulses from the composite received signal;

To provide im- Figure 4 is a diagrammatic representation in i'rontelevation, of an alternate'arrangement of a portion of the transmittingapparatus, adapted for the scanning of three dimensioned subjectsinstead of motion picture film;

Figure 5 is a side elevation of the apparatus illustrated in Fig. 4; and

Figure 6 is a diagrammatic representation of an alternate arrangement ofselecting amplifier, and its 'connections to the receiver scanningsources.

Similar reference numerals refer to similar parts throughout the severalviews.

Referring to Fig. 1, a motion picture illm which is to be transmitted bymy improved method is indicated'at II. This is caused to move uniformlypast an aperture I2 by means o! a suitable mechanism, as by the sprocketI3. It is illuminated by light from a. source I4.

` on a rotary Nipkow disk I 8, which is provided with a concentric ringof small holes near its periphery, and allows light from only oneelemental area of the image to pass through to a photoelectric device I1at any4 instant of time. 'I'he combined motion of the lm and disk thusaccomplishes sequential two-dimensional scanning, and device I'I is thusmade to produce electrical pulses corresponding to lighting of theelementary portions of the illm. Each bright pulse of light causes alarge flow of electrons through the circuit composed of device I'I, aresistor I8, and abattery I9, and causes the potential at the top ofthis resistor at point 20, to become more negative than normal. Let usdefine these pulses for the purpose of this discussion, as image pulses.

The high frequency synchronizing pulse apparatus, which functions toproduce a pulse for each scan of a hole in disk I6 past an imageaperture 2 I, is located at a circumferential point on disk I6, otherthan that-opposite aperture 2|. A source of light 22 illuminates aportion of the ring of holes in the disk, directly opposite an aperture23 and a photoelectric device 24. It

To provide the necessary low frequency synchronizing pulses, preferablyoccurring once for each rotation by, the same mechanism that drives thefilm sprocket I3, by any suitable means, which it has not beenconsidered necessary iso-illustrate. This disk has an aperture t0therethrough, to allow a pulse of light to pass from a light source (notshown) on the opposite side of the disk 'to photoelectric device 28, andthus also produces an abnormally positive potential at 2S on resistor2'I.V

Aperture 2|,vthrough which light transmitted through the film imagepasses. is made slightly narrower than the circumferential 'distancebetween adjacent holes on scanning disk 1 6. Thus, from the time onehole leaves the image held until the next one enters, there'exists ashort interval during which no light can reach the photoelectric deviceI1, and hence its response vat this time corresponds to that of black inthe scale oflimage light intensities. g

Aperture 2l is made of a width, which, circumferentially measured, mayconveniently bemade equal to that of one or two elementary scanningareas; that is, say, one or two eightieths of the distance betweenadjacent disk holes, for a scanning disk containing a ring of eightyholes. This aperture'isv positioned so that light is admitted to itsassociated photoelectric device 24 during the interval between thepassage of the disk holes past the image aperture 2|. There are nearlyeighty such positions possible aroundan eighty hole disk. i i

It was mentioned above, in considering the image pulse producingapparatus, that a bright pulse of -light caused the potential at 20 onresistor i8, to become more negative than normal. Thus an absence oflight or blackness, occurring between each` scan of a hole across theimage, because of the narrowed aperture 2l, will cause this potential tohave its vmaximum positive value. Itv

was further mentioned, in considering the synchronizing apparatus.. thatthe bright flash of light causes a maximum positive-potential to appearat 26 on resistor 21. Points .20 and 26 are connectedk together throughcondensers 3| and 32, of negligible reactance at the frequenciesinvolved, and to the input wire 33 of an amplifier comprising athermionic device 34. At any instant the resultant potential at 33'Willbe the algebraic sum of the potentials of points and 26. Thus for theinstant when the image transmitting apparatus is registering black, andthe synchronizing apparatus is adding a further positive pulse, it willbe seen that the potential at wire 33 corresponds to what may, for thepurpose of this discussion, be called blacker than black. l

The form of this composite signal. is indicated along the vertical axisMN in Fig. 3. The electrical potential represented by the axis MNcorresponds to black in the scanning. The extension of the synchronizingpulses at the right of axis MN, in the positive direction, indicatestheir blacker than black character in the scale. of electricallyrepresented light intensity. The rst synchronizing pulse 35 is shownwider than the others above it, to indicate that it is a l`ow frequencypulse which occurs once for each completely scanned image. Thus, for aneighty-line image, seventy-nine narrowpulses occurbefore the wide pulseis repeated. The amplitude of the synchronizing pulses are shown in Fig.S as being about equal to that of the image pulses. They can be madelarger or smaller as convenient, and are often made of about one-fourththe emplituole of the image pulses.

Since the synchronizing pulses are made to al ways occur at a time whenthe narrowed image aperture insures a black image pulse intensity, itwill be seen that they will he of constant amplitude." If meansare notprovided to establish this constant datum, the synchronizing pulses willbe of varying height, depending upon the light ln-V tensity being'scanned at the instant the pulse occurs; .and consequently they will beof less value in maintaining reliable synchronization.

Referring again to Fig. l, the composite signal of wire I3 is amplled bya quartrode 3Q, and its associated apparatus, in the usual manner exceptas to thefunctionlng of 'a resistor 36 and a condenser I'l, in thescreen grid lead o f the device. Elements I6 and 31 constitute aparallel circuit, having less impedance at high frequencies than at lowfrequencies, as iswell known. In the usual application, the size' ofelements 36 Aand 31 are proportioned so that the impedance of thecombination is negligible for; the highest frequency represented in thewave forms to be amplified; For

this frequency, then, the quartrode will function as usual, with aconstant screen potential. For a low frequency, however, the impedanceof the parallel circuit will be considerable. This causes the -potentialof the screen grid to`decre'ase each' time the control grid becomes lessnegative than usual, si'nce the greater flow of electrons from thefilament to the screen, thus occasioned, produces a greater voltage dropin flowing thru the parallel circuit. The current in the anode circuitof the quartrode is directly affected by the potential of the screen, asis well known, being less for a low' screen potential than for a highone.

The usual effect of the control grid becoming decrease the current, theresultant effect will be the difference between the two. Thus thequartrode will not yamplify low frequencies as well as high frequencies.

Fouriers analysis and experiments show that the high frequencycomponents, in proper phase, of a rectangular or other wave of steepwavefront, account for the sharpness of the wavefront. A device whichaccentuates the high frequency components of a Wave, and preserves theirproper phase, will thus accentuate its rectangularity, and compensatefor imperfections in this regard in other parts of the system.

That the parallel circuit represented byelements 36 and 3'! does notintroduce an appreciable phase shift with frequency, can be seen byexamining its action. For low frequencies, the resistor carries nearlyall the current; and the voltage drop across the impedance is in phasewith the current, and the potential variation of the screen is in directopposition to that of the control grid. For high-frequencies, althoughthe phase. angle may approach 90, the impedance is negligible. Thusnegligible screen voltage variation occurs, and the quartrode 34 ampliesnormally.

It will be appreciated, that any impedance composed to give an inversevariation of magnitude withl frequency; and, ideally, having a phasecharacteristic independent of frequency, can be used in place ofelements 3B and Il.

The composite signal, thus amplified, appears across the terminals of aresistor 38; of phase opiii) posite that of wire 33, and correspondingto the ph of a positive" television image, wherein the brigh portions ofthe image correspond to the positive voltage peaks. As shown in Fig. 1.the amplified signal is carried over wire 3l to a radio transmitter 40,which functions to modulate it upon a radio frequency carrier. in amanner well known to the art. Additional stages of amplification, of thetype described. or of the usual distortionless form, can be addedbetween resistor 34 and wire 39, if required. A

The function of the radio transmitter is to provide means for sendingthe composite signals to a distant receiving station, and it may be ofany suitable type known to the art. It should be noted also that,instead of the transmitter-receiver radio communication channelindicated, a single wire with earth return, or a pair of wires, can beused.

Passing now to a consideration of theV receiving apparatus, as showndiagrammatically in Fig. 2.

i a radio receiver is conventionally shown at 4i.

This apparatus is capable of; intercepting the emissions of transmitter40; demodulating (or detecting) them; and amplifying them if necessary,to the end that substantially the same electric pulses will travel inwires 42 and 43, that travel in wire 3S at the transmitter.

The number of stages of amplification between wire 33, at thetransmitter, and wire 43 at the receiver, is m'ade such that the phaseof the signal in wire 43 corresponds to a "negativ television image;that is, wherein the bright portions of the image correspond to thenegative voltage peaks. Rectangle 44 diagrammatically represents asingle stage, or any odd number of stages, of amplification, which areprovided to change the phase of the image signal to positive, in wire42, as is necessary for the proper operation of the cathode-ray tube 45;since, in this arrangement of apparatus, positive voltage peakscorrespond to maxiunr brilliancy on the screen. These stages can be ofthe usual distortionless type, or of the high frequency accentuaingtype, described above in connection with the transmitting apparatus.

In Fig. 2, rectangles 46 and 41 represent sources of sawtooth scanningenergy, of low and high frequency respectively, provided for theactuation of the cathode-ray image reproducing tube 45. The detailedconstruction and operation of these generators has been fully explainedin my copending application No. 596,711, filed March 4, 1932. Wires 48and 49 represent proper connections to these low and high frequencysources, for effecting synchronization thereof by the application of thevoltage pulses originating in the transmitting apparatus, as fullydescribed in the above cited application. Wires 50 and 5i connect theoutput of these sources to the deflection plates 52 and 53 of thecathode ray tube 45, respectively, for deection of the electronic beamover the fluorescent screen 54 for scanning purposes.

Passing now.to the means for separating the synchronizing pulses fromthe image pulses, thev thermionic vacuum tube 55 and its associatedapparatus, constitute a selecting amplifier, adapted to perform thisfunction. The composite signal of negative television polarity, shownalong the vertical axis MN in Fig. 3, is carried by wire 43 of Fig. 2,as previously explained. A stopping condenser 56 is provided, to removethe direct positive potential applied to the anode of the last tube inreceiver 4I, and to make the separating apparatus unresponsive to lowfrequencies. Condenser Il and resistor I1 compose a high-pass lter,adapted to transmit high frequency energy with less attenuation than lowfrequency energy. It is found in practice that shift of axis. withrespect to maximum energy peaks. is a common form ofcommunication-channel distortion. This causes the peaks to be receivedpartly below, as well as above, the axis: although originated at thetransmitter entirely above the axis. It is found that these extensionsbelow the axis impair the reliability of synchronization of the receiverequipment, by introducing spurious pulses in the synchronizationchannel. Since, however, such peaks are generally of considerableduration, with respect to the time of a synchronizing pulse. they can-beremoved from the synchronization apparatus by making it unresponsive tolow frequencies. Thus condenser 58 is made relatively small, as are thesimilar cooperating condensers l, 59, and 80 in the other portions ofthe synchronizing apparatus.

The potential of the battery 6| is such as to bias the grid of tube 55to cut-off; that is, to reduce its anode current substantially to zero.This action is shown diagrammatically in Fig. 3, where the line NDrepresents the grid-voltage platecurrent characteristic of the tube. Thealternating potential of the composite signal MN is, of course,superimposed on the direct potential of battery 5I. The positivesynchronizing pulses indicated at C in Fig. 3, cause the grid of tube 55to become less negative, and to allow pulses of anode current indicatedat C' to flow from the filament to the anode, and through a resistor 62and a battery 63. The image pulses, causing the grid to become morenegative than the value which causes the anode current to cease, arethus not reproduced in the anode circuit. In this Way the synchronizingpulses are selected from the composite signal.

The synchronizing current pulses C cause negative voltage pulses toappear at the top of resistor 62. These are applied through the wire 49,and the stopping condenser 60, to the high frequency scanning source 41for the synchronization thereof. This output is further amplified by aquartrode 64, which is of the high frequency accentuating type describedabove in considering the transmitting station; and then is applied tothe low frequency source 46 through wire and stopping condenser 59, forthe synchronization thereof.

When thus synchronized, the low and high frequency generators coact toconstantly position the fluorescent spot on the cathode ray tube screen,in the same relative position as that occupied by the scanning disk holein relation to the motion picture film fram'e being scanned at thetransmitter. f

It is not necessary to separate the low and nigh frequency synchronizingpulses, so as to apply each to its proper receiver source. The naturalperiods of the receiver sources cause them to respond, like pendulums ina mechanical system being subjected to mechanical pulses. Only thepulses of periodicity near that of the source, are effective insynchronizing it. It is necessary, however, to provide some sort of highimpedance or unilaterally conductive element, between wires 4B and 49,so that the scanning generators shall not be closely coupled, nor beliable to react upon each other. The addition of the quartrode 64accomplishes this purpose, and, incidentally, also sharpens the pulseapplied to generator 46.

It will be appreciated that sharp pulses are desirable in synchronizingtelevision scanning apparatus. rather than gradual pulses. or energyvariations approaching the sinusoidal; in that a rapid change of enersyacts to cause local action at that instant, regardless of localconditions. whereas a gradual change ot energy acts to cause localaction at one instant for a given local condition, and at a laterinstant when local conditions are less favorable for initiating theaction. It will be understood that thermionic tube 55 can also be a highfrequency accentuating quartrode; or that both oi' the thermionic tubescan be distortionless amplifiers, and still function as selectingampliiler and. isolating amplier respectively. It will be furtherunderstood that the rectangularity or the pulses delivered by the hereindisclosed separating means, exceeds that of devices employingwavefllters, or other frequency discriminating devices. Such devicesoften deliver quasi-sinusoidalenergy for the pulse inputs.

An alternate arrangement of connections from the selecting amplifier 65to the scanning generators 46 and 41. may consist in insertingimpedances, that are relatively high at the operating frequencies ofthese sources, in one or both ot the wires 48 and 49. It is possible toachieve proper synchronization of, and absence o! interaction between,the scanning source, by placing resistors in wires 4B and/or 49. Thesefunction to reduce the amplitude oi the synchronizing pulses, as well asto isolate the sources; but to a less amount than the isolation gained,if resis' tors be located in both wires. The reduced pulse amplitude iscompensated for by increasing the pulse amplitude at the transmitter,increasing the amplification of device 56,'or in other ways that will beapparent to those skilled`in the art.

Another alternate arrangement of connections, lies in inserting diodesin one or each of the wires 48 and 49, with the cathodes connected tothe top of resistor 62 and anodes toward the scanning generators. Thesynchronizing voltage pulses at resistor 62 are negative, and thus lowerthe potential of the diode cathode with respect to its anode, Fallowingan. electron flow between the two. In the reverse direction, however,negative voltage pulses, arising from the operation of the scanninggenerators, and attenuated by the small stopping condensers 59 and/or80, are incapable of flowing through the diode, since they act to makethe anode potential more negative than that of the cathode. It isevident that other unilaterally conductive devices can bc used ln placeof this diode.

A further alternative arrangement of the output circuits is illustratedin Fig. 6. Here a quartrode, 65, is adapted to give two independentoutput circuits by providing a resistor 66, in the screen circuit. Thesynchronizing output for one source appears at thev top of resistor 62and is led oil through wire 49, as before, while wire 48, connectingYwith the other generating source, is connected to the top of resistor66. It will be appreciated that as many output circuits as desired canbe secured, by placing the proper number of output. electrodes in thethermionic device 65.

It also is possible to `utilize this invention when the polarity of thephotoelectric devices 2'4 and 26, and of battery 25, are reversed. Inthis case, instead'of the outputs of these devices adding to that of theimage pulse produced in photo electric device I1,I during the time whenit is not receiving light, to give a "blacker than black compositesignal. they subtract from it. Their amplitude is made considerablygreater than the amplitude of the maximum pulse produced in the imagedevice, by increasing the intensity of the light sources 22 and thatback oi' aperture 30, for example, thus causing the pulses to be "whiterthan white" in the scale ot electrically represented light intensities.A composite signal of this nature is shown along vertical axis KL inFig. 3. The whiter than white" peaks are shown at G in this figure.

in separating these pulses from the composite signal at the receiver,the number of stages of amplification between wires 33, at thetransmitter, and wire 4I, at the receiver, ismade such that the'phaseoi' the signal in wire 43 corresponds to a positive television image.This is as indicated on axis KL in Fig. 3. The potential of battery 6iis increased over its previous value, by an amount suilicient to causethe image pulse variations -to'occur still more negatively than thecut-oi! potential, oi' tube 55. The greater distance of axis KL from theaxis of zero grid potential OIp, with respect to that of axis MN,indicates diagrammatically the proper condition. Itwill be seen thatpulses G will only be reproduced in the anode current as pulses C', andthat the operation of the remainder of the apparatus will be the same aspreviously explained.

It is possible to remove the whiter than white" pulse from the input tothe cathode-ray intensity control connection 42 in Fig. 2, by providingtwo stages of -ampliilcation in the device represented by rectangle 44,and two additional stages of amplification represented by dottedrectangle 11 after resistor 82, the output of the last mentioned stagesbeing connected to wire 42. The phase of the synchronizing pulses ofvoltage being negative at resistor 62, the phase two stages beyond itwill also be negative. The phase of the. composite signal, in wire 43being positive, the phase two stages beyond it will also be positive.Thus, when the two outputs are combined in wire 42, it will be seen thatthe negative synchronizing pulses from the synchronizing channel willtend to cancel the original positive pulses present in the continuationof the composite channel. 'I'he relative amplication of the twotwo-stage ampliers is adjusted in practice until cancellation isobtained, or it may be -made such that a negative pulse predominates',vwhich extinguishes the spot on the cathode-ray tube screen during thesychronlzlng action. 'Ihe two amplifiers serve to isolate theconnections between channels, and to prevent interaction between inputand output of a single stage, as would exist if resistor 62 wasconnected directly to wire 42.

An alternate arrangement for removing the positive pulse lies inproviding the cathode-ray tube with two electrodes capable oi'modulating the electron beam thereof. Two control elements of the typeshown at 61 in Fig. 2 are provided, one' being connected to wire 42 asusual,- and the other tothe output of the synchronizing channel. The twotwo-stage amplifiers need not be employed in this arrangement. It willbe further understood that the anode 68 of the cathode-ray tube, asshown, can have its action modulated by the output of the synchronizingchannel, by inserting a resistor in lead 69, and connecting said outputto the top thereof, and vice versa, wherein the wire 42 is thereconnected, and said output is connected to control electrode 61.

An alternate arrangement of the transmitter scanning equipment, adaptedto scan three dii image pulse-producing photoelectric devices. thismanner 'till mensional objects, such as living persons, is showndiagrammatically in Figs. 4 and 5. At lil is represented theconventional Nipkow disk with spirally arranged holes 'l i. shown)passes through an aperture l2, narrowed as was aperture 2i in Fig. l,and is focused on` Light from a source (not through any of the spirallyarranged holes, and .Y

also through the hole i6, spaced from the usual spiral series, and insuch a position that it can pass light to the photoelectric device atthe compietion of an entire scan of the object.

The device comprising aperture 14, hole 18, and photoelectric device 'l5can, of course, be connected in either a positive or negative manner, togive either blacker than black, or whiter than white synchronizingpulses. In case the latter pulses are to be produced, the light sourcelli can he arranged to shine through the disk to suitable fixedreflecting surfaces, for reflection to In both synchronizing and imagepulses may be optically combined, and be impressed 'upon a singleelectrical channel.

ri'he illustrated wiring connections, diagrams, and conventionalrepresentations of apparatus, not specifically mentioned in theforegoing discussion, but necessary for a complete practical system,will be fully understood by those familiar with the art involved.

Having thus fully claim:

l. In television apparatus, means for removing synchronizing pulses irom a communication channel carrying a composite signal, comprising; athermionic device adapted to separate said pulses from said signal, byhaving its input circuit biased to a potential near that which wouldcause its constant output circuit current to ybecome zero; and means forrta-inserting the separated pulses in a continuationof the compositesignal channel, with a polarity opposite to that of the original pulses.

y 2. in television apparatus, means for removing the effect of a pulse,present ina composite signal, upon the intensity of an electron stream,cornprising; means adapted to separate saidpulse from said signal; meansfor reversing the phase of said pulse; and dual means for influencingthe electron stream; one of the last said means heing' adapted foriniiuencing said stream in accordance with the variations of saidsignal; the other of the last said means being adapted for influencingsaid stream in accordance with the reversed phase of said pulsevariations.

3. Apparatus for transmitting a motion picture hlm by television,comprising; means for scanning the film, and for producing image pulsesthereby; means for producing, in a single channel of communicationbetween the transmitter and receiver, a signal composed of said imagepulses and of synchronizing pulses of substantially rec disclosed myinvention, I

tangular shape and of constant amplitude; means for producing one suchsynchronizing pulse for each passage of a lm frame-linepastthe scanningaperture, and for each scan of the scanning element across the film;means for transmitting said composite signal from a transmitter to areceiver; means comprising a negatively biased thermionic device forseparating said synchronizing pulses from said image pulses; meanscomprising a separate output electrode in said thermionic device,connected to each source of scanning energy at said receiver for thesynchronization thereof; and means for applying said image pulses to animage forming device co-acting with said sources of scanning energy, toreproduce the image.

4. Television synchronizing apparatus comprising; a source ofquasi-rectangular synchronizing pulses; a thermionicdevice adapted toamplify said pulses, and having an input electrode, an output electrode,and a coacting auxiliary electrode; scanning equipment connected incircuit with said output electrode; and an impedance element connectedin circuit with said auxiliary electrode, and adapted to change inimpedance with changes in frequency of the energy applied to thethermionic device, whereby the rectangularity of the pulses flowing inthe output circuit of said thermionic device may be increased.

5. In a television system which includes a plurality of scanning devicesat the receiving station,

synchronizing means at the receiving station comprising; a thermionicdevice having an input electrode, and a plurality of output electrodesadapted for supplying identical outputs; the output electrodes beingindependently connected to the said plurality of scanning devices forsynchro nization thereof; said scanning devices being adapted forscanning in different directions, and

n to co-operate to form a single image.

6. A method of television synchronization which comprises; producing aseries of substantially rectangular synchronizing pulses of constantamplitude, one for each traverse of the scanning element across the eldof view, and occupying a very small fraction of the time of onetraverse; producing another series of substantially rectangularsynchronizing pulses of constant amplitude, one for each completetraverse of the field of view, having the same amplitude and a durationseveral times greater than the first mentioned series; the pulses ofeach oi. said series being of negative polarity; continuously producingimage pulses of positive polarity; combining all said pulses, andtransmitting them from the station of origin to a receiving station in asingle channel of communication; reversing the phase station,substantially without distortion, by a thermionic amplifying device;applying all oi said pulses, in their saidreversed phases, to a singlenon-oscillating therrnionic device which has a high negative bias, andwhich is adapted to amplify and reproduce only the two series ofsynchronizing pulses, at the same amplitude, in its output circuit; andapplying the whole amplitude of said reproduced synchronizing pulses toeach of two separate self -oscillating scanning devices at the receivingstation for the synchronization thereof; the last said scanning devicesbeing operated at the frequency of repetition of said synchronizingpulses respectively.

HARRY R. LUBCKE.

of all of `said pulses at the receiving

